The present invention relates to preparations that are suitable for the manufacture of wound dressings or bandages and comprise at least one alginate and at least one antiseptically active substance.
The invention furthermore relates to processes for the production of antiseptically active alginate preparations, and the use thereof.
The salts of alginic acid are called alginates. Alginic acid is a colorless, carboxyl groups-containing polysaccharide of 1,4-glycosidally linked D-mannuronic acid units with occasional insertions of L-guluronic acid, and falls into the group of the polyuronic acids. Alginic acid can account for up to 40 wt. % of the dry matter of brown algae. The alkali salts of alginic acid, the ammonium salt of alginic acid, and the magnesium salt of alginic acid are water-soluble. In particular, sodium alginate, also called algine, is of great importance as a thickening agent, emulsifier or emulsion stabilizer, and as a basis for gels, in the food, pharmaceutical and cosmetics industries. By contrast, calcium alginate and zinc alginate are water-insoluble, just as is alginic acid. By adding water-insoluble calcium alginate to sodium alginate gels it is possible to increase the viscosity of the latter.
The use of calcium alginate for the production of alginate fibers, and of wound dressings made of alginate fibers, is already known. Alginate fibers are produced by extracting alginic acid from algae by means of a soda solution. The resultant sodium alginate solution is purified and pressed into a precipitation bath containing a weakly acid CaCl2 solution.
European patent application publication EP 0 586 260 A1 describes alginate gels in the form of a fibrous paste, which has an alginate content of 2 to 11 wt. %. and which is produced by treating water-insoluble or water-swellable alginate fibers with an aqueous solution of a solubilizing salt.
U.S. Pat. No. 5,470,576 discloses a process for the production of alginate-containing wound dressings, wherein a soft, absorbent fabric is impregnated with an alginate by immersing the fabric into an aqueous sodium alginate solution, to which calcium chloride is subsequently added in order to precipitate calcium alginate. These wound dressings are intended to have a haemostatic effect upon contact with the wound.
European Patent EP 0 783 605 B1 describes wound dressings which contain alginate fibers and are produced by co-spinning and solidification of an alginate and a water-soluble carboxymethyl cellulose. The alginate has a cross-linked form, and the alginate from which the fibers are co-spun has a G-content of at least 35 wt. %.
European patent application publication EP 1 435 247 A1 relates to a multilayer wound dressing comprising a fabric of alginate fibers and a layer which is not to be brought into contact with the wound and contains a superabsorbent.
Wound dressings or bandages of natural alginate fibers have good absorption capacity for wound exudate. Because of this, wound dressings of this type are also suitable for the wound management of highly exuding wounds, such as ulcers, decubital ulcers and fresh split-thickness skin removals, as well as for the wound management of infected wounds. Their high exudation absorptivity enables dressings to be changed at greater intervals.
It is particularly advantageous that wound dressings of alginate fibers form a gel upon contact with wound exudate or blood. This enables the wound dressing to conform to the contours of the wound and also to bind bacteria, contained in the exudate, in the gel. The wound is continuously maintained in a moist condition, epithelium can develop readily, and, due to an optimal microclimate, wound healing is accelerated.
Another advantage of wound dressings or bandages of natural alginate fibers is that they do not stick to the skin. Consequently, the young tissue is not damaged when the dressing or bandage is changed, and the healing process is not interrupted.
Wounds contaminated with or infected by pathogens must, however, be treated antiseptically as well, because:                infection may develop as long as the wound is colonized,        the wound healing process remains incomplete, or is completed with a delay only, as long as the wound remains infected,        the infection of the wound may spread and lead to sepsis, and        in the case of a colonization of the wound with multi-resistant germs, the spreading of the pathogens must be prevented.        
In the case of burn wounds, too, there is a necessity of early prevention of wound infections, especially where contamination of larger wound areas is to be expected.
There is thus a need for wound dressings or bandages for wound management that enable antiseptic wound treatment.
However, the treatment of acute and chronic wounds with local therapeutics, especially with antiseptics, is presently regarded as being appropriate only for special indications, since many of the established antiseptics are considered unacceptable on assessment of their cost-benefit-risk ratio. Modern local antiseptics, which in contrast to the above, afford a broad spectrum of activity and good tolerability are, for example, octenidine and polyhexanide (=polyhexamethylene biguanide; PHMB). Short-term application of octenidine is supported especially in cases of microbially contaminated acute wounds, whereas polyhexanide is recommended instead for repeated applications on chronically slow-healing or sensitive wounds due to its comparatively slow onset of action. A disadvantage of the use of polyhexanide, however, is the fact that this antiseptic loses its efficacy in the presence even of small quantities of negatively charged ions.
International application publication WO 02/36866 A1 discloses polysaccharide fibers having water-absorbent properties, preferably of alginate or of a combination of alginate and another polysaccharide material, for example absorption-enhancing carboxymethyl cellulose, which fibers contain a silver compound as an antimicrobially active agent. WO 02/36866 A1 also describes wound dressings made from these polysaccharide fibers.
International application publication WO 03/022317 A1 describes an antibacterial wound dressing based on gel-forming fibers, such as carboxymethyl cellulose or alginate fibers, to which silver ions are bound uniformly, via part of the available reversible binding sites for cations.
The use of silver and silver compounds in wound treatment is considered largely outdated, because of the short-term stability of the commonly employed preparations, because of possible absorption of silver ions, and because of superficial destruction of the skin by protein coagulation.